Expression of iron-related proteins in the duodenum is up-regulated in patients with chronic inflammatory disorders

Low Serum Hepcidin Levels in Patients with Ulcerative Colitis - Implications for Treatment of Co-existent Iron-Deficiency Anemia

Ulcerative colitis (UC) is often associated with anemia. Hepcidin, the central regulator of iron homeostasis, is known to be induced by inflammation and suppressed by anemia. It is not clear how hepcidin is affected in those with UC, when both inflammation and anemia may co-exist.Such knowledge may hold implications for treatment. Hematological and iron-related parameters, C-reactive protein (CRP), growth differentiation factor 15 (GDF-15) and erythroferrone (ERFE) (erythroid regulators of hepcidin) levels were estimated in blood from those with UC and in control subjects. Values for hematological and iron-related parameters showed evidence of iron-deficiency and resultant anemia, in patients with UC. The presence of UC was significantly associated with inflammation. Serum levels of ERFE, but not of GDF-15, were significantly higher in patients with UC than in control patients, while hepcidin levels were significantly lower. Serum hepcidin concentrations in patients with UC correlated positively with serum iron, ferritin and GDF-15, and negatively with serum ERFE. The iron status and serum hepcidin levels in UC patients with co-existent anemia were significantly lower and serum ERFE values significantly higher than in those with UC without anemia. The effect of anemia on hepcidin predominated over that of inflammation in patients with UC, resulting in suppressed hepcidin levels. This effect is possibly mediated through erythroferrone. We suggest that a serum hepcidin-guided approach may be useful to guide use of oral iron supplements to treat co-existent iron-deficiency anemia in patients with UC and other chronic inflammatory diseases.

Iron homeostasis is dysregulated, but the iron-hepcidin axis is functional, in chronic liver disease

BACKGROUND

Perturbations in iron homeostasis have been reported to be associated with irreversible liver injury in chronic liver disease (CLD). However, it is not clear whether liver dysfunction per se underlies such dysregulation or whether other factors also contribute to it. This study attempted to examine the issues involved.

METHODS

Patients diagnosed to have chronic liver disease (n = 63), who underwent a medically-indicated upper gastrointestinal endoscopy, were the subjects of this study. Patients with dyspepsia, who underwent such a procedure, and were found to have no endoscopic abnormalities, were used as control subjects (n = 49). Duodenal mucosal samples were obtained to study mRNA and protein levels of duodenal proteins involved in iron absorption. A blood sample was also obtained for estimation of hematological, iron-related, inflammatory and liver function-related parameters.

RESULTS

Patients with CLD had impaired liver function, anemia of inflammation and lower serum levels of hepcidin than control subjects. Gene (mRNA) expression levels of duodenal ferroportin and duodenal cytochrome b (proteins involved in iron absorption) were decreased, while that of divalent metal transporter-1 (DMT-1) was unchanged. Protein expression of DMT-1 was, however, decreased while that of ferroportin was unchanged. In the CLD group, serum hepcidin was predicted independently by serum ferritin and hemoglobin, but not by C-reactive protein (a marker of inflammation). CLD patients with serum ferritin greater than 300 μg/dL had significantly greater liver dysfunction (as indicated by significantly higher serum concentrations of bilirubin, AST and ALT, and MELD scores), higher serum concentrations of CRP and hepcidin, and higher ferroportin protein expression, than those with serum ferritin ≤ 300 μg/dL.

CONCLUSIONS

In patients with CLD, anemia of inflammation and low serum hepcidin levels were found to paradoxically co-exist. Expression of duodenal proteins involved in iron absorption were either decreased or unaltered in these patients. The hepcidin response to higher body iron levels and/or inflammation appeared to be functional in these patients, despite the presence of liver disease.

Increased DMT1 and FPN1 expression with enhanced iron absorption in ulcerative colitis human colon

Iron deficiency anemia is a common complication of ulcerative colitis (UC) that can profoundly impact quality of life. Most iron absorption occurs in the duodenum via divalent metal transporter 1 (DMT1)-mediated uptake and ferroportin-1 (FPN1)-mediated export across the apical and basolateral membranes, respectively. However, the colon also contains iron transporters and can participate in iron absorption. Studies have shown increased duodenal DMT1 and FPN1 in patients with UC, but there is conflicting evidence about whether expression is altered in UC colon. We hypothesized that expression of colonic DMT1 and FPN1 will also increase to compensate for iron deficiency. Quantitative RT-PCR and Western blot analyses were performed on duodenal and colonic segmental (right colon, transverse colon, left colon, and rectum) biopsies obtained during colonoscopy. DMT1 mRNA and protein abundances in colonic segments were approximately equal to those in the duodenum, whereas colonic FPN1 mRNA and protein abundances of colonic segments were about one-quarter of those of the duodenum. DMT1 specific mRNA and protein abundances were increased twofold, whereas FPN1 mRNA and protein expressions were increased fivefold in UC distal colon. Immunofluorescence studies revealed enhanced expression of apical membrane- and basolateral membrane-localized DMT1 and FPN1 in UC human colon, respectively. Increased DMT1 expression was associated with enhanced 2-(3-carbamimidoylsulfanylmethyl-benzyl)-isothiourea (CISMBI, DMT1 specific inhibitor)-sensitive ⁵⁹Fe uptake in UC human colon. We conclude from these results that patients with active UC have increased expression of colonic iron transporters and increased iron absorption, which may be targeted in the treatment of UC-related anemia.

Investigation of manganese homeostasis in dogs with anaemia and chronic enteropathy

Lethargy is a frequent and important clinical feature of anaemia; however, it does not absolutely correlate with the severity of anaemia. Manganese is efficiently absorbed through the gastrointestinal tract via divalent metal transporter 1 (DMT1), which is also responsible for iron transport. DMT1 is upregulated in iron deficiency (ID). Increased manganese concentrations are reported in ID anaemia (IDA) in various species. Manganese is neurotoxic and therefore may contribute to lethargy observed in some anaemic patients. In addition, anaemia and ID are common in human inflammatory bowel disease. Little is known about how anaemia influences manganese metabolism in veterinary patients and how common is anaemia in dogs with chronic enteropathy (CE). If elevated manganese concentrations are found, then potentially neurotoxicity may be contributing to morbidity in these cases. The objectives of this study were to investigate the hypothesis that whole blood manganese concentrations would be increased in dogs with anaemia, particularly in dogs with confirmed IDA, and that anaemia would be common in canine CE. Medical records from 2012-2016 were reviewed for dogs with CE that were anaemic, as well as dogs with confirmed IDA, where a sample suitable for manganese analysis was held in an archive. Manganese concentration was measured in whole blood from: 11 anaemic dogs with CE, 6 dogs with IDA, 9 non-anaemic ill controls, and 12 healthy controls. Mann-Whitney U and Kruskal-Wallis tests with post-test Dunn's multiple comparisons tests were performed, with P<0.05 considered significant. The prevalence of anaemia in canine CE was 20.6% (33/160). Manganese concentrations were significantly different between all groups (P=0.0001) and higher in non-anaemic than anaemic dogs (P=0.0078). Manganese concentrations were also higher in healthy compared to ill controls (P<0.0001), anaemic dogs with CE (P=0.0056) and to dogs with IDA (P=0.0001). No differences were observed between anaemic dogs with CE, IDA and ill controls. Although anaemia was frequently observed in canine CE, the hypothesis that dogs with anaemia would have increased manganese concentrations, possibly contributing to a lethargic state was not supported. Further research is warranted to understand the influence of anaemia on whole blood manganese.

Asthma as a disruption in iron homeostasis

Over several decades, asthma has evolved from being recognized as a single disease to include a diverse group of phenotypes with dissimilar natural histories, pathophysiologies, responses to treatment, and distinctive molecular pathways. With the application of Occam's razor to asthma, it is proposed that there is one cause underlying the numerous phenotypes of this disease and that the responsible molecular pathway is a deficiency of iron in the lung tissues. This deficiency can be either absolute (e.g. asthma in the neonate and during both pregnancy and menstruation) or functional (e.g. asthma associated with infections, smoking, and obesity). Comparable associations between asthma co-morbidity (e.g. eczema, urticaria, restless leg syndrome, and pulmonary hypertension) with iron deficiency support such a shared mechanistic pathway. Therapies directed at asthma demonstrate a capacity to impact iron homeostasis, further strengthening the relationship. Finally, pathophysiologic events producing asthma, including inflammation, increases in Th2 cells, and muscle contraction, can correlate with iron availability. Recognition of a potential association between asthma and an absolute and/or functional iron deficiency suggests specific therapeutic interventions including inhaled iron.

Iron Homeostasis and Inflammatory Status in Mice Deficient for the Cystic Fibrosis Transmembrane Regulator

BACKGROUND

Cystic Fibrosis (CF) is a frequent and lethal autosomal recessive disease caused by mutations in the gene encoding the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). Patients with CF suffer from chronic infections and severe inflammation, which lead to progressive pulmonary and gut diseases. Recently, an expanding body of evidence has suggested that iron homeostasis was abnormal in CF with, in particular, systemic iron deficiency and iron sequestration in the epithelium airway. The molecular mechanisms responsible for iron dysregulation and the relationship with inflammation in CF are unknown.

METHODS AND RESULTS

We assessed the impact of CFTR deficiency on systemic and tissue iron homeostasis as well as inflammation in wildtype and CFTR knockout (KO) mice. First, in contrast to the systemic and intestinal inflammation we observed in the CFTR KO mice, we reported the absence of lung phenotype with regards to both inflammation and iron status. Second, we showed a significant decrease of plasma ferritin levels in the KO mice, as in CF patients, likely caused by a decrease in spleen ferritin levels. However, we measured unchanged plasma iron levels in the KO mice that may be explained by increased intestinal iron absorption.

CONCLUSION

These results indicate that in CF, the lung do not predominantly contributes to the systemic ferritin deficiency and we propose the spleen as the major organ responsible for hypoferritinemia in the KO mouse. These results should provide a better understanding of iron dysregulation in CF patients where treating or not iron deficiency remains a challenging question.

Ferrous sulfate, but not iron polymaltose complex, aggravates local and systemic inflammation and oxidative stress in dextran sodium sulfate-induced colitis in rats

Background and aims

Iron deficiency is common in inflammatory bowel disease, yet oral iron therapy may worsen the disease symptoms and increase systemic and local oxidative stress. The aim of this study was to compare the effects of oral ferrous sulfate and iron polymaltose complex on inflammatory and oxidative stress markers in colitic rats.

Methods

Animals were divided into four groups with ten animals each. Rats of three groups received dextran sodium sulfate to induce colitis and animals of two of these groups received 5 mg iron/kg of body weight a day, as ferrous sulfate or iron polymaltose complex, for 7 days. Gross colon anatomy, histology of colon and liver, stainings of L-ferritin, Prussian blue, hepcidin, tumor necrosis factor-α, and interleukin-6, as well serum levels of liver enzymes, inflammatory markers, and iron markers, were assessed.

Results

Body weight, gross anatomy, crypt injury and inflammation scores, inflammatory parameters in liver and colon, as well as serum and liver hepcidin levels were not significantly different between colitic animals without iron treatment and colitic animals treated with iron polymaltose complex. In contrast, ferrous sulfate treatment caused significant worsening of these parameters. As opposed to ferrous sulfate, iron polymaltose complex caused less or no additional oxidative stress in the colon and liver compared to colitic animals without iron treatment.

Conclusion

Iron polymaltose complex had negligible effects on colonic tissue erosion, local or systemic oxidative stress, and local or systemic inflammation, even at high therapeutic doses, and may thus represent a valuable oral treatment of iron deficiency in inflammatory bowel disease.

The role of iron in the skin and cutaneous wound healing

In this review article we discuss current knowledge about iron in the skin and the cutaneous wound healing process. Iron plays a key role in both oxidative stress and photo-induced skin damage. The main causes of oxidative stress in the skin include reactive oxygen species (ROS) generated in the skin by ultraviolet (UVA) 320-400 nm portion of the UVA spectrum and biologically available iron. We also discuss the relationships between iron deficiency, anemia and cutaneous wound healing. Studies looking at this fall into two distinct groups. Early studies investigated the effect of anemia on wound healing using a variety of experimental methodology to establish anemia or iron deficiency and focused on wound-strength rather than effect on macroscopic healing or re-epithelialization. More recent animal studies have investigated novel treatments aimed at correcting the effects of systemic iron deficiency and localized iron overload. Iron overload is associated with local cutaneous iron deposition, which has numerous deleterious effects in chronic venous disease and hereditary hemochromatosis. Iron plays a key role in chronic ulceration and conditions such as rheumatoid arthritis (RA) and Lupus Erythematosus are associated with both anemia of chronic disease and dysregulation of local cutaneous iron hemostasis. Iron is a potential therapeutic target in the skin by application of topical iron chelators and novel pharmacological agents, and in delayed cutaneous wound healing by treatment of iron deficiency or underlying systemic inflammation.

Intestinal inflammation modulates expression of the iron-regulating hormone hepcidin depending on erythropoietic activity and the commensal microbiota

States of chronic inflammation such as inflammatory bowel disease are often associated with dysregulated iron metabolism and the consequent development of an anemia that is caused by maldistribution of iron. Abnormally elevated expression of the hormone hepcidin, the central regulator of systemic iron homeostasis, has been implicated in these abnormalities. However, the mechanisms that regulate hepcidin expression in conditions such as inflammatory bowel disease are not completely understood. To clarify this issue, we studied hepcidin expression in mouse models of colitis. We found that dextran sulfate sodium-induced colitis inhibited hepcidin expression in wild-type mice but upregulated it in IL-10-deficient animals. We identified two mechanisms contributing to this difference. Firstly, erythropoietic activity, as indicated by serum erythropoietin concentrations and splenic erythropoiesis, was higher in the wild-type mice, and pharmacologic inhibition of erythropoiesis prevented colitis-associated hepcidin downregulation in these animals. Secondly, the IL-10 knockout mice had higher expression of multiple inflammatory genes in the liver, including several controlled by STAT3, a key regulator of hepcidin. The results of cohousing and fecal transplantation experiments indicated that the microbiota was involved in modulating the expression of hepcidin and other STAT3-dependent hepatic genes in the context of intestinal inflammation. Our observations thus demonstrate the importance of erythropoietic activity and the microbiota in influencing hepcidin expression during colitis and provide insight into the dysregulated iron homeostasis seen in inflammatory diseases.